The present invention relates to constructions of a coupling arrangement for connecting drill jigs for use in conjunction with "Hardinge" type collet and indexing fixtures.
A Hardinge fixture is a well known and commonly used fixture which is employed in conjunction with hand and/or automatic drilling machines to secure workpieces in position for drilling. The fixture comprises a base which is fastened to the bed plate of a drilling machine and will support a collet adapted to hold a workpiece about its periphery so that the drill can pass through its opposing faces. The collet is supported in a turret which is rotatable about its central axis so as to index the workpiece in proper alignment with the drill. Hardinge fixtures can be used in vertical drill or horizontal drilling machines.
Notwithstanding the versatility of the Hardinge fixture, it is difficult to drill a circular arrangement of holes in disk type or flat workpieces concentric with the center thereof, since the turret operation of the Hardinge fixture is rotatable about the collet axis only and because the drill, being flexible, may not center itself on its own true axis.
Moreover, to drill circular arrangements of holes of different diameters, it has been necessary to custom make jigs for each such arrangment.